Quick Reference Guide

PowerConnect B-Series TI24X Configuration Guide 679
53-1002269-02
Configuring OSPF
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The bandwidth for interfaces that consist of more than one physical port is calculated as follows:
• Trunk group – The combined bandwidth of all the ports.
• Virtual interface – The combined bandwidth of all the ports in the port-based VLAN that
contains the virtual interface.
The default reference bandwidth is 100 Mbps. You can change the reference bandwidth to a value
from 1 – 4294967.
If a change to the reference bandwidth results in a cost change to an interface, the Layer 3 Switch
sends a link-state update to update the costs of interfaces advertised by the Layer 3 Switch.
NOTE
If you specify the cost for an individual interface, the cost you specify overrides the cost calculated
by the software.
Interface types to which the reference bandwidth does not apply
Some interface types are not affected by the reference bandwidth and always have the same cost
regardless of the reference bandwidth in use:
• The cost of a loopback interface is always 0.
• The cost of a virtual link is calculated using the Shortest Path First (SPF) algorithm and is not
affected by the auto-cost feature.
• The bandwidth for tunnel interfaces is 9 Kbps and is not affected by the auto-cost feature.
Changing the reference bandwidth
To change the reference bandwidth, enter a command such as the following at the OSPF
configuration level of the CLI.
PowerConnect(config-ospf-router)# auto-cost reference-bandwidth 500
The reference bandwidth specified in this example results in the following costs:
• 10 Mbps port cost = 500/10 = 50
• 100 Mbps port cost = 500/100 = 5
• 1000 Mbps port cost = 500/1000 = 0.5, which is rounded up to 1
• 155 Mbps port cost = 500/155 = 3.23, which is rounded up to 4
• 622 Mbps port cost = 500/622 = 0.80, which is rounded up to 1
• 2488 Mbps port cost = 500/2488 = 0.20, which is rounded up to 1
The costs for 10 Mbps, 100 Mbps, and 155 Mbps ports change as a result of the changed
reference bandwidth. Costs for higher-speed interfaces remain the same.
Syntax: [no] auto-cost reference-bandwidth <num>
The <num> parameter specifies the reference bandwidth and can be a value from 1 – 4294967.
The default is 100. For 10 Gbps OSPF interfaces, in order to differentiate the costs between 100
Mbps, 1000 Mbps, and 10,000 Mbps interfaces, set the auto-cost reference bandwidth to 10000,
whereby each slower link is given a higher cost
To restore the reference bandwidth to its default value and thus restore the default costs of
interfaces to their default values, enter the following command.